This invention generally relates to chemical sampling, and more specifically, to a man-portable chemical and biological sampler including a combination impact collector and fan, and integrated chemical and/or biological sensors.
Sample acquisition and sample analysis are frequently performed as two disparate processes, since in situations that are not time critical, it is generally acceptable to take one or more samples, and to transport those samples to an analytical laboratory for analysis. Environmental air quality and water quality samples are often handled in such a fashion. However, there are many situations in which the ability to take an environmental air sample, and to analyze that sample immediately, are critical to health and safety. Measuring the air quality in poorly ventilated spaces such as mines, determining the presence of chemical and/or biological agents on the battlefield, or after an actual or suspected terrorist attack, are examples of situations in which sampling and analysis should be performed as quickly as possible, preferably by employing an integrated sampling and sensing apparatus that can provide and immediate indication of a life threatening substance in the environment.
There are many examples in the art of integrated sampling and detection apparatus. Drxc3xa4ger-Tubes, which are manufactured by Drxc3xa4gerwerk A G, Ltibeck (http://www.draeger.com), are one well-known example of an integrated sampling and detection system. These devices are used to measure the concentration of specific gases and vapors in real time. Over 200 different Drxc3xa4ger tubes are available for measuring more than 500 different contaminants. The design and principle of operation of each Drxc3xa4ger-Tubes is the same in every case. A chemical reagent system is housed in an enclosed clear glass tube; and the reagent system reacts by changing color when exposed to a specific gas or vapor. The concentration of the substance is characterized by the length of discoloration within the tube and can be read off directly from a scale printed on the glass tube. Different amounts of air must be drawn through the tube, depending on the type and sensitivity of the reagent systems used. The volume of ambient air that must be drawn through the tube by a Drxc3xa4ger pump is stated on each tube. This prior art chemical sampling and detection system thus consists of a Drxc3xa4ger-Tube and a corresponding Drxc3xa4ger pump.
Other integrated air sampling and detection systems specifically designed to detect trace gases in air include electrochemical sensors for the measurement of gases such as CO, H2S, O2, Cl2, SO2, NO2 etc, infrared sensors for the measurement of CO2, CH4 or alkanes, and catalytic (pellistor) gas sensors for measuring flammable gases.
One drawback of the prior art integrated sampling and detection devices is that the target of interest is often present in the sampled environment in extremely small amounts. Acquiring a good sample of a reagent at low concentrations is problematic. Even if the sensor is capable of detecting minute levels of an agent of interest, without a high quality and readily obtainable representative sample, the capabilities of the sensing system are inefficiently utilized. Even worse, an inadequate sample of a hazardous material can cause a detection device to falsely indicate the absence of that material.
The difficulty in obtaining a good quality sample is particularly evident with respect to sampling for airborne particulates or aerosols. For example, aerosols comprising small droplets of liquid dispersed into air are not easily analyzed unless the aerosol materials are separated from the air and concentrated in a sample that can then be accurately analyzed. As used herein, the term xe2x80x9cparticulatesxe2x80x9d (and its singular form xe2x80x9cparticulatexe2x80x9d) will be understood to include aerosols, liquids, solids, or semi-solids that are sufficiently small to be dispersed within and carried about in air or other gases and may include inorganic or organic chemicals, or living materials, e.g., bacterial cells or spores. Also, the term particulates refers to solids or semi-solids introduced into a liquid that is then dispersed within air as an aerosol mist so that the solids are carried within the liquid droplets comprising the aerosol mist.
Generally, it is difficult to identify materials comprising particulates entrained in a gaseous fluid unless the particulates can be collected and concentrated in a specimen suitable for analysis by separating them from the air or other gaseous fluid. One significant application in which extremely low levels of particulates need to be sampled and analyzed quickly is to provide combat troops with individual sampling units, that either include their own sensor, or which can be read in the field under combat conditions.
Particle impact devices are commonly used for collecting particulates from gaseous streams in which they are dispersed. These collectors xe2x80x9csweepxe2x80x9d a large volume of air, and concentrate any particulates collected to provide a high quality representative sample. Several different types of particle impact collectors are available. Functionally, these particle impact collectors generally employ circuitous paths with many abrupt changes of direction along the passages through which a particulate-laden fluid flows. The particulates, being substantially more massive than the molecules of the fluid in which they are entrained, fail to negotiate the abrupt turns in these passages and are thus separated from the moving fluid stream, collecting on the surfaces that they impact. In the presently available types of particle impact collectors, there is generally a trade off between simplicity and efficiency.
Stationary impact collectors that employ a fan to force air against the impact surface are relatively simple, but are somewhat less efficient than would be desired. Rotating arm collectors are more efficient, yet are also more complex, in that they require both the rotating impact collector and a fan to be independently driven.
It would therefore be desirable to provide a simple and efficient particle impact collector that is capable of yielding a high quality representative sample of particulates or aerosols. Such a device is described in commonly assigned, co-pending U.S. patent application, Ser. No. 09/265,619, entitled xe2x80x9cImpact Particulate Collector Using A Rotary Impeller For Collecting Particulates And Moving A Fluid,xe2x80x9d which was filed Mar. 10, 1999, the specification and drawings of which are hereby specifically incorporated herein by reference. It would further be desirable to integrate such a sampling device with a sensor to provide a portable system capable of rapidly detecting the presence of an agent of interest, so that the sample that is collected does not need to be sent to a laboratory facility for analysis. The prior art does not teach or suggest a portable integrated sampler and sensor unit that employs a rotary impeller used to both collect particulates and move a fluid through the unit.
In accord with the present invention, a method and apparatus for separating particulates from a fluid are defined. A significant facet of the present invention is the use of a combined impact collector and fan, employed to both force a gaseous fluid into the sampling unit, and to provide an impact surface onto which particulates are impacted and collected.
According to the method of the present invention, a combined impact collector and fan is provided. The combined impact collector and fan is disposed within a cavity having a port and is rotatable about an axis. Rotation of the combined impact collector and fan draws a particulate-laden fluid into the cavity. Particulates are separated from the fluid when they impact on the combined impact collector and fan as it rotates. The combined impact collector and fan is then rinsed with a rinse fluid, and the xe2x80x9crinsatexe2x80x9d (i.e., particulates from the combined impact collector and fan) are collected in the rinse fluid.
In at least one embodiment, the combined impact collector and fan is rinsed with the rinse fluid while it is rotating. Preferably, such an embodiment collects the rinsate in a rinse fluid reservoir, and the rinse fluid is recycled.
In a different embodiment, the combined impact collector and fan is rinsed with a rinse fluid only after the combined impact collector and fan has been rotated for a predefined period of time. Preferably, the predefined period of time is a function of the type of particulate being collected.
When the particulates being collected comprise biological organisms, the rinse fluid is preferably not toxic to biological organisms, so that a collected sample can be cultured to determine a result. However, this characteristic of the rinse fluid is unimportant and is not a requirement if the collected sample will be analyzed by methods other than culturing.
In another embodiment of the method of the present invention, the step of rinsing includes utilizing a rinse fluid that includes a surfactant to reduce a surface tension of the rinse fluid, thereby increasing an efficiency of the rinse fluid in carrying the rinsate away from the combined impact collector and fan during the rinsing step.
Preferably, in one embodiment, the combined impact collector and fan is a disposable element, so that the disposable element is removed from a prime mover that is included for rotating the combined impact collector and fan, before the rinse step. When employing such a disposable element, a rinse station is provided, and the step of rinsing includes the step of placing the combined impact collector and fan into the rinse station. Preferably, a rinse cassette is also provided, so that the step of placing the combined impact collector and fan into the rinse station includes the steps of inserting the combined impact collector and fan into the rinse cassette, and then placing the rinse cassette into the rinse station. In one embodiment, the step of rinsing includes the step of rotating the rinse cassette during rinsing, to aid in removing the particulates from the combined impact collector and fan. In another embodiment, the step of rinsing includes the step of applying an ultrasonic pulse to the rinse cassette during rinsing, to aid in removing the particulates from the combined impact collector.
In yet another embodiment, a decontamination fluid is provided, and the combined impact collector and the cavity are flushed with the decontamination fluid before rotating the combined impact collector. Preferably, the decontamination solution is either a bleach solution or a hydrogen peroxide solution. Any fluid lines in fluid communication with the combined impact collector and the cavity are also preferably decontaminated with the decontamination fluid.
A programmable electronic controller enables a user to selectively control a length of time during which the combined impact collector is rotating. A user is also enabled to selectively control the rinsing step, to selectively rinse either for a duration of the rotation of the combined impact collector, or to rinse after the combined impact collector has stopped rotating, or to rinse such that the rinsate is reused as a rinsing fluid, thereby recycling the rinsate. The user can also select a time period for the rinse. When a decontamination fluid is provided, a user is preferably enabled to selectively decontaminate the combined impact collector and the cavity prior to rotating the combined impact collector, or to decontaminate the combined impact collector and the cavity after rinsing and after the rinsate has been collected, or to decontaminate the combined impact collector and the cavity after a user-defined number of rotating, rinsing, and collecting cycles has occurred.
In still other embodiments, an analytical unit is included with the collector, and the method further includes the step of utilizing the analytical unit to test the rinsate. In one embodiment, the analytical unit includes a test strip capable of detecting anthrax. Preferably, the analytical unit is a disposable unit specifically adapted to detect a specific substance. In some embodiments, the analytical unit is a disposable micro-fluidic unit. One such micro-fluidic analytical unit employs a cytometry-based detection system, while another such analytical unit uses a fluorescence-based detection system.
Another aspect of the present invention is a portable impact particle collector for separating particulates from a gaseous fluid in which the particulates are entrained. Such apparatus includes a prime mover having a drive shaft that is drivingly rotated, a power supply capable of energizing the prime mover, and a primary housing that substantially encloses the prime mover and the power supply. This apparatus further includes a combined impact collector and fan that is coupled to the drive shaft and rotated thereby, and a fluid passage for conveying the gaseous fluid in which the particulates are entrained into the combined impact collector and fan. The fluid passage includes at least one inlet and at least one outlet. The apparatus further includes at least one user selectable control operatively connected to the prime mover, adapted to enable a user to selectively energize the prime mover.
In one embodiment, the combined impact collector and fan includes a plurality of arcuate-shaped vanes. Also, one configuration of the combined impact collector and fan includes a ferromagnetic element that is magnetically coupled to the prime mover.
In yet another embodiment, the combined impact collector and fan is disposed outside of the primary housing. Preferably, the primary housing then includes at least one surface feature to aid in positioning the combined impact collector and fan. A secondary housing substantially encloses the combined impact collector and fan and is preferably pivotally connected to the primary housing.
In one form of the present invention, the combined impact collector and fan is a consumable unit, adapted to be replaced by a user with a new unit after a defined period of use. In this form, the fluid passage and the combined impact collector and fan comprise an integrated unit. Preferably, the integrated unit includes a fluid passage fabricated from an upper portion and a lower portion of a housing, the combined impact collector and fan being disposed between the upper portion and the lower portion and being freely rotatable therein. Also preferably, at least one of the lower portion and the combined impact collector and fan are fabricated from a self-lubricating material to ensure that the combined impact collector and fan can freely rotate when disposed within the lower portion of the housing without requiring bearings or additional lubricants to reduce friction between the lower portion of the housing and the combined impact collector and fan.
In still another embodiment of the portable impact particle collector, an electronic controller is electrically coupled to the at least one control and to the prime mover. The electronic controller is substantially enclosed within the primary housing.
To aid in removing impacted particulates from the combined impact collector and fan, a rinse fluid reservoir adapted to contain a volume of rinse fluid and a first fluid line in fluid communication with the rinse fluid reservoir and the combined impact collector and fan is provided in one embodiment. Also included is a sample collection reservoir adapted to contain a volume of rinse fluid that has been used to rinse particulates from the combined impact collector and fan, and a second fluid line in fluid communication with the sample collection reservoir and the combined impact collector and fan.
A decontamination fluid reservoir, adapted to contain a fluid capable of decontaminating the combined impact collector, and a decontamination fluid line in fluid communication with the decontamination fluid reservoir and the combined impact collector and fan are included in one embodiment of the invention. The rinse fluid reservoir, the decontamination fluid reservoir, and the collection fluid reservoir are preferably disposed in a disposable fluid cartridge, which is substantially disposed outside the primary housing, while the first fluid line, the second fluid line, and the decontamination fluid line are substantially disposed within the primary housing. A plurality of valves and a pump are included so that a flow of fluid within the first fluid line, the second fluid line, and the decontamination fluid line can be independently controlled.
One configuration of the present invention includes a diagnostic cartridge, adapted to determine if the first fluid line and the second fluid line are functioning properly. Preferably, the diagnostic cartridge includes a plurality of fluid reservoirs. Markings on one or more of the fluid reservoirs indicate whether the first fluid line and the second fluid line are functioning properly.
The rinse fluid reservoir and the sample collection reservoir are combined into a single reservoir in another configuration of the present invention, such that the rinse fluid is recycled. Preferably, the rinse fluid includes water and may include a detergent to reduce surface tension, and to enhance the removal of particulates adhering to the combined impact collector. Optionally, the rinse fluid further includes a phosphate buffer solution capable of sustaining the viability of microorganism particulates, such that the microorganisms can be cultured.
In some embodiments, the combined impact collector is coated with a substance to which the particulates adhere when the substance is dry, the substance releasing the particulates when wetted with a rinse fluid. In some embodiments, the substance includes at least one of gelatin and sugar.
In embodiments of the present invention in which the combined impact collector is a disposable unit, a rinse station is preferably provided to enable a liquid sample to be removed from the combined impact collector. A rinse cartridge can be included to contain the disposable combined impact collector and any fluid used in the rinse station. The rinse station preferably includes either a prime mover to spin the disposable combined impact collector during rinsing, a vibrator to vibrate the disposable combined impact collector during rinsing, or an ultrasonic unit to apply an ultrasonic pulse to the disposable combined impact collector during rinsing, to aid in removing particulates from the combined impact collector.